Subject:
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USB tower flow control question
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 16 Jan 2002 18:21:01 GMT
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Original-From:
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PC CHAN <pc.chan@alcatel.comNOMORESPAM>
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Viewed:
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663 times
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Hi there,
The more serious problem observed when trying to get legousbtower,
usb-uhci and nqc to work togeher was that the tower hanged after one
complete round trip. (nqc and legousbtower works with uhci on my setup
but not with usb-uhci.)
Usb-uhci managed to transport the first echo command and responses
between the RCX brick and nqc correctly (7 bytes forth and 7 bytes back).
The tower then stopped flashing when usb-uhci seemed dma'ing happily as
usual. That's not right. On rmmod and insmod usb-uhci, the tower came
into life again for another round trip.
Why would the tower stop working, Could it be jammed because of traffic?
Would the tower do flow control and how?
Legousbtower is using interrupt urb's to transport data while it also
uses control urb's to configure the tower. The control urb's works OK
for multiple rounds without the need for restarting.
Interrupt handling in usb-uhci could be a bit off in timing. I am still
trying to follow its logics.
I have an USB camera (OV511) working with usb-uhci, but it is does not
use any interrupt's urb's.
I wonder if anybody has success in any usb driver that uses interrupt
urb's with usb-uhci.
Regards,
P.C.
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Message has 1 Reply:
 | | Re: USB tower flow control question
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| (...) Yup - this is what happens for me also. (...) Yup (although often needs a physical unplug/replug as well for me). (...) I believe it's not the tower, it's the USB subsystem that is 'jammed'. The 0.5 version of the legousbtower.c driver is not (...) (23 years ago, 17-Jan-02, to lugnet.robotics)
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